Alkylene oxides are known for a multiplicity of utilities. Ethylene oxide, for example, is used to produce ethylene glycol, which is used as an automotive coolant, as antifreeze, and in preparing polyester fibers and resins, nonionic surfactants, glycol ethers, ethanolamines, and polyethylene polyether polyols. Propylene oxide is used to produce propylene glycol and polypropylene polyether polyols, which are used in polyurethane polymer applications.
The production of alkylene oxides via catalytic epoxidation of olefins in the presence of oxygen using supported silver based catalysts is known. By introducing a promoting amount of rhenium in the silver catalyst, the efficiency of the epoxidation reaction can be greatly improved. Epoxidation reactions are typically carried out in presence of gaseous reaction promoters such as chlorinated hydrocarbons which increases the efficiency of the reaction. For silver catalysts containing rhenium, in addition to increasing efficiency, increasing the amount of chlorinated hydrocarbons typically increases the activity of the epoxidation reaction. As a result the reaction can be conducted at lower temperatures while maintaining constant alkylene oxide production.
The prior art teaches that epoxidation reactions can be run at maximum efficiency at a temperature by adjusting the concentration of the chlorinated hydrocarbons. This can lead to running the reaction at a higher than necessary (or desirable) temperature, leading to increased risk of over-chlorination of the catalyst and hence deactivation of the catalyst, and also cause difficulty in maintaining a target ethylene oxide production rate due to the catalyst's strong activity dependence on chlorine level.
It is desirable to provide an improved method of producing ethylene oxide which resolves some of the issues associated with operating the epoxidation reaction at optimal efficiency.